The invention relates to ultra-wideband (UWB) radar motion sensors and more particularly to the power and wiring configuration thereof.
Many sensors function as simple switches that require no external power. Such sensors are considered passive since they do not dissipate power. An example of a passive sensor is a bimetallic thermostat that closes a switch contact at a particular temperature.
Other sensors are active devices which consume power from an external source. Electrical connections are therefore required. An example of an active sensor is an electronic thermostat whereby the switch is relay driven by a circuit that requires external power.
Passive switches are most desirable since no external power is required, thereby simplifying wiring to the sensor.
A motion sensor based on ultra-wideband (UWB) radar is described in U.S. patent application Ser. No. 08/044,717, now U.S. Pat. No. 5,361,070. UWB radar range is determined by a pulse-echo interval. For motion detection the sensors operate by staring at a fixed range and then sensing any change in the averaged radar reflectivity at that range. The sensors have a wide variety of applications including security systems; switches for lights, doors, appliances, machines, etc.; medical devices; and automotive collision sensors.
In all applications of the impulse radar motion sensor, it is desirable to employ a low power configuration having a simple wiring scheme. Ideally, only a single wire pair from a power source is required.